compute network - Troubleshooting

Network Troubleshooting

Troubleshooting computers and networks is a combination of art and science and the only way to get a really good at it is by doing it a lot of practice, practice.

We’ll learn to check quickly for problems in the “super simple stuff” category.

So let’s start step by step troubleshooting of computer and network:

Narrowing Down the Problem:

It’s a great strategy to start by narrowing things down to the source of problem. To help you achieve that goal, it’s always best to ask right questions. Some list of questions to ask yourself to narrowing down the problem:

  • Did you check the super simple stuff (SSS)?
  • Is hardware or software causing the problem?
  • Is it a workstation or server problem?
  • Which segments of the network are affected?
  • Can you test the network from end to end to confirm connectivity?
  • Are there any cabling issues?


Let’s see all this question in details:

1) Did You Check the Super Simple Stuff?

Some points you should remember when you are performing Super Simple Stuff.

  • Check to ensure login procedures and rights.
  • Look for link lights and collision lights.
  • Check all power switches, cords, and adapters.
  • Look for user errors.


2) Is Hardware or Software Causing the Problem?

Solutions to hardware problems, usually involve one of three things:

  • Changing hardware settings.
  • Updating device drivers.
  • Replacing dead hardware

Is It a Workstation or a Server Problem?

The first thing you’ve got to determine when troubleshooting this kind of problem is whether it’s only one person Or a whole group that’s been affected. If the answer is only one person solving the issue will be pretty straightforward. If more than that, and your problem probably involves a chunk of the network, like a segment then problem is with server. Now check on server, what is problem, solve this all client computers will work fine.

Which Segments of the Network Are Affected?

Figuring this one out can be a little tough. If multiple segments are affected, you may be dealing with a network address conflict. If you’re running Transmission Control Protocol/Internet Protocol (TCP/IP), remember that IP addresses must be unique across an entire network. So if two of your segments have the same static IP subnet addresses assigned, then problem with duplicate IP errors.

Is It Bad Cabling?

When you figured out problem is not with network segment, server, router, switches you must examine the relevant cabling. Are the cables properly connected to the correct port? If the problem is with bad cabling then it’s very easy to fix.

Network troubleshooting Steps:

For the troubleshooting network there are seven main steps you need to remember

  • Identify the problem.
  • Establish a theory of probable cause.
  • Test the theory to determine cause.
  • Establish a plan of action to resolve the problem and identify potential effects.
  • Implement the solution or escalate as necessary.
  • Verify full system functionality, and if applicable, implement preventative measures.
  • Document findings, actions, and outcomes


Let’s assume a situation, user called you and said I can’t connect to the server on intranet and also can’t connect to internet.

Step 1: Identify the problem:

Before you look in this problem, ask some questions to users, the right questions can get you far along this path and really help clarify the situation.

Identifying the problem involves steps that together constitute information gathering.

Gather Information by Questioning Users:

A good way to start is by asking the user the following questions:

  • Exactly which part of the Internet can’t you access? A particular website? A. certain address? A type of website? None of it at all?
  • Can you use your web browser?
  • Is it possible to duplicate the problem?
  • Ask the user if they can ping the server and talk them through doing that.
  • Ask the user to try to telnet or FTP to an internal server to verify local network connectivity, if they don’t know how, talk them through it.
  • If there are multiple complaints of problems occurring, look for the big stuff first, then isolate and approach each problem individually.
IPv4 Result

It’s good that worked, so the server is up. You just ping the server, it doesn’t mean host is 100% up and running.


Step2: Establish a Theory of problem Cause:

In our previous scenario we’ve determined the cause is probably improperly configured DNS lookup on the workstation. The next thing to do is to verify the configuration and probably reconfigure DNS on the workstation.

Here some points you need to keep in mind:

  • Port speed
  • Port duplex mismatch
  • Mismatched MTU
  • Incorrect virtual local area network (VLAN)
  • In correct IP address/duplicate IP address
  • Wrong gateway.
  • Wrong DNS
  • Wrong subnet mast
  • Incorrect interface/interface misconfiguration

Step 3: Test the Theory to Determine Cause:

In this step we are going to implement out determined theory in previous step.

Let’s look into the matter by first checking the IP configuration of the host that just happens to include DNS information. We can use the ipconfig/all command to show the IP Configuration. The /all switch will give us the DNS information that we need.

Step 4: Establish a plan of Action to Resolve the Problem and Identify Potential Effects

Now that you’ve identified some possible changes, you’ve got to follow through and test your solution to see if you really solved the problem. In this case, you ask the user to try to access the intranet server. Basically, you just ask the user to try doing whatever it was they couldn’t do.

If it works then problem solve. If not, try other troubleshooting methods.


Step 5: Implement the Solution or Escalate as Necessary:

You can’t fix every single network problem that could possibly happen in the universe, they actually do expect you to get pretty close to determine exactly what the problem is. And if you can’t fix it, you’ll be expected to know how to escalate it and to whom. You are only good as your resources.

It you can’t fix it, then escalate your problem ASAP, because escalation will save you from big impact.

You need to esca1ate these problem to a senior network engineer who has the additional experience and knowledge required to resolve the problems.

Some of the problems you should escalate:

      • Switching loops
      • Missing routes
      • Routing loops
      • Routing problems
      • MTU black hole
      • Bad Module
      • Proxy Address Resolution Protocol (ARP)
      • Broadcast storms
      • NIC Teaming misconfiguration
      • Power failures/power anomalies